1. Field of the Disclosure
The present disclosure relates generally to filtration devices and systems, and particularly to liquid recovery filter assemblies having inlet and outlet ports and, in some embodiments, vent, drain and/or recovery ports for the drainage and recovery of filtered liquids from the filter housing and enclosed filter after filtering operations. More particularly, the disclosure relates to apparatus and methods to retrieve liquids retained in filtration apparatus after filtration processes.
2. Description of the Related Art
Innumerable filtration devices and systems have been developed for the cleaning and purification of a wide range of gases and liquids. One area that requires extremely high quality filtration is in the field of pharmaceutical manufacture, where a number of different liquids are involved in the manufacturing processes of a large number of drugs and medications. These various liquids are often quite costly to produce, and as a result, much effort and expense is expended to recover such liquids in a sterile manner during the manufacturing process, insofar as practicable.
During liquid filtration processes, liquid is passed through the filter assembly(s) and the filtered liquid is recovered from the downstream or outlet side of the enclosed filter element. In one type of filter element used, the filter element conventionally has a generally toroidal configuration wherein the unfiltered liquid passes through the filter element from outside the filter and through the filter material to a hollow inner core. Other filter element configurations may also be used in a similar manner or in a reverse manner flowing from the inner core to the outside of the element. One problem with such filter configurations is that when the filtration process is completed, there is a volume of purified, filtered liquid still resident in the filter element, as well as unfiltered liquid remaining within the filter housing and outside the filter element. These liquids are often quite valuable, as noted above. Discarding these liquids when the filtration process is completed or interrupted results in the loss of a considerable amount of valuable and usable liquid, particularly after numerous filtration processes.
One method used to remove the resident filtered liquids is to introduce pressurized gas into the system to force the liquids out of the filter assembly. This approach, although effective, is problematic due to the relatively high bubble points of the filter materials used for many specific applications, including many of the filtration processes common in the pharmaceutical industry. When the filtration material of the filter element is wetted (as is typically the case after use for liquid processing), bulk gas flow through the filter element is blocked by the wetted filter material at pressures below the bubble point pressure, as is commonly known in the art. Therefore, gas pressurized to pressures below the bubble point pressure cannot efficiently clear the downstream (filtered) liquid.
Filter materials with pore sizes about and below 0.2 microns have particularly high bubble point pressures that require relatively high gas pressures (typically greater than 40 psi for membrane-based absolute-rated filters wet with water or other liquid of similar surface tension) to evacuate the liquid in the wetted filter material. Even filter materials with pore sizes greater than 0.2 microns can have bubble points higher than the pressure limits of other components that commonly make up filter assemblies. The introduction of high pressure gas can compromise the physical and functional integrity of the filter element and/or filter assembly by, for example, causing the filter element to separate from its attachment points, or causing the filter element to physically break and potentially compromise the desired separation of unfiltered and filtered liquids, allowing them to mix downstream. Mixture of the filtered and unfiltered liquids would invariably compromise the intended purity or sterility of the filtered liquid. In addition, assemblies using, for example, barbed connectors for hoses can experience hose breakage or separation from the barbed connectors when gas at a relatively high pressure is introduced into the filtering apparatus. Moreover, pressure-sensitive components such as those incorporating thin films have pressure ratings and operational limits well below the bubble points of many filter materials.
What is needed is a filter recovery system that provides a means to remove valuable filtered liquids from a filter apparatus in a sterile or otherwise contamination-free manner. What is also needed is a filter recovery system that permits the use of a gas applied at a relatively low pressure to effectively remove resident filtered liquids while maintaining the sterility and/or any other required characteristics of the liquids in the downstream locations within, and external to (further downstream of), a filter assembly. These and other problems are solved by the disclosed liquid recovery filter apparatus as shown and described in the appended drawings, disclosure summary, and more particularly in the detailed description of the disclosure.